What component of the power system is most vulnerable to damage from extended operation at frequencies above or below 60 Hz?

The correct choice highlights the vulnerability of low pressure turbine stage blades to damage when operated at frequencies deviating from the standard 60 Hz. This stems from the nature of turbine operation, particularly the resonance characteristics and vibrational modes associated with turbine blades.

Turbine blades, especially those in low pressure stages, are designed and optimized for specific operational frequencies related to the synchronous speed of the turbine. When the operational frequency is significantly altered, the dynamic forces acting on the blades can lead to resonance conditions that can cause excessive vibrations, fatigue, or even failure. Operating at a frequency well above or below the designed parameters can compromise the structural integrity of these blades, leading to catastrophic mechanical issues.

In contrast, while transformers, synchronous motors, and induction motors do have operational limits and varying levels of sensitivity to frequency changes, their design often allows them to handle some frequency deviations without immediate catastrophic failure. For instance, transformers generally can tolerate a wider range of frequencies without risking damage, serving longer operational life under varied conditions. Synchronous and induction motors also exhibit a range of tolerances regarding frequency variations, although they may face performance issues, such as overheating or efficiency loss.

These differences in how components respond to frequency changes underline why low pressure turbine stage blades are particularly vulnerable